The present invention relates to MR (magnetic resonance) imaging method and apparatus for an image diagnosis system which utilizes an NMR (nuclear magnetic resonance) phenomenon.
In this kind of MR imaging apparatus, an image of the human head by way of example is generally displayed representing a field of view of 250 mm.times.250 mm by 256.times.256 pixels. In recent years, however, it has been desired to display an image with a much higher definition. For example, the following techniques (1) and (2) are known:
(1) a part of a field of view which is a so-called region of interest is displayed over the whole of a display screen; and
(2) the whole of a field of view is taken in or picked up with 512.times.512 pixels and an image is displayed with the same number of pixels.
However, in the technique (1), since the size of one pixel is only enlarged, the resolution is unchanged or not improved notwithstanding that the region of interest is displayed in an enlarged form. In the case of the technique (2), since the number of pixels is doubled, a doubled time is required for taking in or acquiring data. In general, the S/N ratio and the area of a pixel have the relation of ##EQU1## and the S/N ratio and the number of times of data accumulation or integration for averaging of data performed for improvement in S/N ratio have the relation of ##EQU2## Accordingly, in the technique (2), since the area of a pixel decreases to quarter, the S/N ratio decreases or deteriorates to half. Accordingly, in order to improve the S/N ratio to the same order as that in the case where the number of pixels is 256.times.256, the S/N ratio must be doubled. This means that the number of times of data accumulation should be performed four times. As a result, a data acquisition time required has an increase by eight times.